Heating apparatus



Nov. 2, 1965 .1.1. FANNON, JR 3,215,418

Y l HEATING APPARATUS Filed oct. 15, 1961 2 sheets-sheet 1 Wn I T; I* Oii ATTORN EY Nov. 2, 1965 J. J. FANNON, JR 3,215,418

HEATING APPARATUS Filed Oct. 13, 1961 2 Sheets-Sheet 2 l Ihl/ INVENTORJohn J. Fonnon,Jr.

ATTORNEY 6 United States Patent O 3,215,418 HEATING APPARATUS John J.Fannon, Jr., Grosse Pointe Park, Mich., assignor to Hupp Corporation,Cleveland, Ohio, a corporation of Ohio Filed Oct. 13, 1961, Ser. No.144,923 4 Claims. (Cl. 263-8) The present invention relates to ovens,components thereof and more particularly to ovens and heating apparat-usfor drying and curing fluid finishes or coatings applied to a basematerial which will be Iheated upon irradiation by infrared radiation.As used in this specification and the appended claims a fluid finish orcoating means a material which contains a liquid and a residue which isapplied to a surface of a .base material, usually metallic, with theresidue either in solution or suspension in the liquid and from whichthe liquid may be volatilized by heating to leave the residue fixed tothe surface of the base. While the drying of certain fluid nishesinvolves merely removal of the solvent and in all cases removal of thesolvent is a major factor, it is only part of the process in paintbaking. Most coatings are converted from liquid to solid partly byevaporation of solvent and partly fby a chemical reaction, such aspolymerization or oxidation which takes place at high temperatures or isaccelerated by heat. Therefore, the function of the oven is not only toremove the solvent, but to heat the coating to such a temperature as isrequired to cure the finish, and t0 maintain this temperature longenough for the necessary curing reaction to take place. The actualtemperature required at the Work piece surface for optimum resultsdepends on the composition of the coating, but for most organic finishesis in the range of 300 F. to 600 F. Too low a temperature at the workpiece either prolongs the baking time required or results in a softcoat. Too high a temperature may burn off the finish or cause it to .bebrittle or peeloff. A coated work piece as used herein means an articleto which a fluid finish or coating has been applied to one or moreentire surfaces thereof or to any portion or portions of said surface,as for example for protective, decorative and/or informative purposesand, depending upon the context may refer to such a work piece eitherbefore or after the liquid has been removed and the residue cured byheat. A Work piece may -be either a member of predetermined dimensionssuch as a sheet or of indefinite dimensions such as a strip fed from aroll.

It has been found that infrared radiant energy from high temperaturesources impinging directly on the coated parts is a most effective andefficient means for baking various types of finishes, and, for highproduction, the heat concentration (B ttu. per square foot) must be keptas high as possible. Very high concentrations can be obtained by usinggas-fired infrared generators. Electrically -generated infrared being ofthe near short WaveV vtype is reflected as a lighting and does notpenetrate beyond the reflective surface of the -uncured coating. Gasgenerated infrared is immediately converted to heat at the instant ofimpingement upon the coating with little or noV reflection, due Vto thefact that gas infrared is of the far infrared of long wave length whichis particularly effective to become absorbed at a high rate rather thanreflected by the highly reflective moisture presenting surface of theuncured coating. From the viewpoint of long life of the generators, ithas been found that gas burning infrared generators utilizing theprinciples described in United States Patent No. 2,775,294issuedDecember 25, 1956 to Gunther Schwank, particularly with the improvementsand modifications as described in my co-pending application Serial No.50,421 filed August -1 8, 1960 for Heating Apparatus and Method, produceexcellent results.

When sheets or strips of metal coated with fluid finish 3,215,418Patented Nov. 2, 1965 ice containing solvents are passed through theinfrared beams emitted by a series of such infrared generators, arrangedso that their radiation beam is directed toward the coated surface, heatwill be transferred to the coated surface very efliciently. The basicproblem is that of removal of the solvent vapors While heating theWorkpieces rapidly to la suitable temperature to cune the finishproperly in a mini-Y mum length of time. While the apparatus and methodof my aforesaid co-pending application produces a very good solution tothis problem, a large volume of air is required to evacuate thevolatiles and the energy potentially availf able in the combustiblevolatiles of the coating is not utilized.

Contrary to thel principles of the invention of my aforesaid co-pendingapplication, the present invention contemplates the provision of asubstantially oxygen free atmospheric blanket overlying the coated workpieces while they are irradiated through the blanket to cure theircoating. This blanket is most easily and effectively achieved in accordwith this invention by positioning the gas burning infrared generatorbanks closely adjacent, in the order of two to three inches, the path ofwork piece movement through the oven and providing a sub-atmosphericpressure fat the sides of the bank of generators. With this arrangement, the products of combustion of the generators ilovv over thesurface of the work pieces toward the sides of the generator bank andform a substantially oxygen free blanket over the work pieces. When sucha blanket is formed the combustible volatiles in the Work piece coating,upon evaporation, immediately enter the substantially oxygen freeblanket. These volatilized particles have a relatively high velocity in`the direction nornal to the coated work piece surface, that is towardthe radiant Wall of the generator bank. The particles of the products ofcombustion forming the substantially oxygen free blanket have arelatively low velocity in a path generally parallel to the Work piecevcoated surface. As a result, the volatile particles are prevented fromigniting adjacent the Work piece coated surface and pass through theblanket toward the radiant Wall of the generator bank. The generatorbank is supplied with an amount of primary air slightly in excess ofthat required for complete combstion of the gaseous fuel. As a result,when the combustible volatiles approach the radiant wall of thegenerator bank, they ignite and combine with the slightly excess oxygenin the primary air. The burning volatiles in this ymanner producesvadditional infrared radiation which in part is directed directly towardthe work piece and in part toward the radiant Wall of the generatorbank. This burning of the vola'- tiles thus increases the normaloperating temperature of the generator bank radiant Wall,- improves itsefliciency and augments the radiation from it tovvard the Work piecesthus increasing the overall efliciency of the oven and eliminating thecombustible volatiles as an explosive hazard.

The primary object of the' present invention is to provide an improvedapparatus for curing coated work pieces by which the coated Work piecesIareY blanketd with a substantially oxygen free atmosphere Whilesubjected to infrared irradiation to heat the work piece and its coatingto the curing temperature of the coating to prevent igniti'on of thecombustible volatiles in the coating at the coated Work piece surfaceduring the coating curing and by which the combustible volatiles areburned under controlled conditions in a position to augment the heatingeffect of the source of infrared radiation.

l More particularly it is an object of this invention to provide animproved apparatus for curing coated work pieces in which the coatedwork piece is irradiated with infrared radiation from a gas burninginfrared generator through a substantially oxygen free workpieceblanketing atmosphere composed of the products of combustion from suchgenerator.

A further object of this invention is to provide an improved method ofand apparatus for curing coated work pices by infrared irradiation ofthe work pieces from a gas burning infrared generator source in whichcombustion of the combustible volatiles in the coating is precludedadjacent the work piece by a blanketing substantially oxygen freeatmosphere composed of combustion products from the infrared source andis effected adjacent the infrared source t augment the heating action ofsuch source.

A further object of this invention is to provide an im- Iproved-apparatus for curing work piece coatings by infrared irradiation inwhich the work piece is blanketed by a substantially oxygen freeatmosphere during its radiation to preclude combustion of thecombustible volatiles in the coating adjacent the work piece coatedsurface.

A further object of this invention is to provide an irnproved apparatusfor and method of curing work piece coatings by infrared irradiation inwhich the combustible coating solvents are burned in a position toprovide infrared radiant energy for heating of the work pieces tothereby increase efficiency and eliminate the hazard of explosion of thecombustible volatiles.

A further object of this invention is to provide apparatus for dryingcoated work pieces by irradiation with infrared radiation from a sourceat a temperature in the order of 1650 F. to 2300 F. through anatmosphere having a sufficiently low oxygen content that ignition ofvolatilized solvents close to the work pieces is precluded.

More specifically, it is an object of this invention to provide a gasburning infrared generator type drying apparatu-s of improvedconstruction wherein cooling air is evacuated from the apparatus overthe generator housing structure to thereby cool said structure andwherein products of combustion are evacuated from between the generatorsand the work pieces to thereby maintain a low oxygen atmospheretherebetween.

A further important object of this invention is to provide an improvedgas burning infrared generator equipped drying oven in which the radiantface of the radiant generators is located a distance from the workpieces such that a low oxygen atmosphere is maintained therebetweenwhereby combustion of volatiles will take place only at said radiantface.

A further object of this invention is to provide a drying oven apparatuswherein radiant generators of the tile type 'are so located relative toa conveyor carrying work pieces therethrough that an atmosphere isestablished and maintained adjacent the work pieces of suiiiciently lowoxygen content to preclude combustion of volatiles and wherein apre-mixed gaseous fuel is supplied to said radiant generators whichcontains sufficient oxygen to completely burn the fuel which is suppliedthereto and containing only suicient excess oxygen to effect completecombustion of the volatilized solvents released from the work pieces assuch volatiles approach the radiant faces of the generator.

These and other objects of this invention will become more fullyapparent by reference to the appended claims and as the followingdetailed description proceeds in reference to the accompanying drawingswherein:

FIGURE 1 is a side elevational view, partially in section, of an ovenembodying and operable in accord with the principles of the presentinvention;

FIGURE 2 is a top plan View of the 4oven of FIGURE A1; and

FIGURE 3 is a sectional view substantially along the line 3-3 of FIGURE1.

Referring now to the drawings in detail and particularly to FIGURES 1and 2I the oven 10 :of the present in- Avention comprises -alongitudinal elongated housing 12 having four sections 14, 16, 18 and 20arranged in end to end relation. Work pieces, usually in the form offlat sheets, are fed through the open sections 14, 16, 18 and 20 by aconveyor 22 comprising a plurality of heat re- Cil sistant cables 24extending in a continuous path defined by guide rollers 26, 28, 30 and32 fixed to the shafts 34, 36, 38 and 40 respectively. One of the shafts34-40, such as shaft 38, is motor driven by a motor (not shown) to causethe cables 24 to continuously feed about the rollers 26-32. The workpieces to be fed through the oven 10 are placed on the inlet end -of theconveyor 22 above the rollers 26 manually or by any suitable automaticmeans and are fed along the forward run of the conveyor 22 betweenrollers 26 and 28 to the discharge end of the conveyor 22 above rollers28 from which they are removed by suitable means such as a furtherconveyor.

Disposed within each of the housing sections 14, 16, 18 and 20 above theforward runner of the conveyor 22 between the rollers 26 and 28 is abank of gas burning infrared generators 42. Each bank of infraredgenerators preferably comprises twenty longitudinally extending parallelrows of infrared generators 44, there being preferably three infraredgenerators in each row in each section of the housing. The generators 44of the central fourteen rows in each :section are supplied with premixedgaseous fuel and air sufficient for complete combustion of the gaseousfuel through a common manifold structure such as indicated at 46 inFIGURE 3, the three front rows of infrared generators of all fourhousing sections 1420 are preferably fed through a common manifoldstructure such as indicated at 48 and the three rearmost rows ofinfrared generators 44 are preferably fed from a common manifold such asindicated at 50 for all four sections of the housing, as is fullydisclosed and described in my aforesaid co-pending application.

As is best shown in FIGURE 3, the housing sections 14-20 each comprise aplurality of metallic uprights 52 each of channel shape cross sectioninterconnected by longitudinally extending metallic frame members 54,56, 58 and 60 each of channel shape cross section and by transverselyextending frame members (not shown). The sides of the housing sectionsare closed by sheet metal cover plates 62 and 64 secured to the uprights52.

The infrared generators 44, which as indicated above are preferably ofone of they improved reected heat resistant constructions disclosed inmy aforesaid co-pending application, are mounted within -a framestructure 66 which is supported by transversely extending support bars68 which in turn are adjustably suspended by tie bolts 70 from thelongitudinally extending channel shaped frame members 58 and 60. Thebolts 70 are adjusted so that the radiant bottom wall 72 defined by thecoplanar radiant faces of the infrared generators 44 is parallel to thetop surface of conveyor 22 and spaced from the top coated surface 74 ofthe coated Work pieces 76 carried by conveyor 22 a dist-ance in theorder of two to three inches. Each of the banks of generators thusproduces a generally rectangular downwardly directed beam of infraredradiation which is intercepted by the work pieces as they are 'moved bythe conveyor through the oven 10.

By this arrangement, the products of combustion of the infraredgenerators 44 form a substantially oxygen free blanket over the topsurface 74 of the work pieces 76 so that the combustible volatiles inthe coating of the work piece 76 cannot ignite adjacent the top surface74 of the work piece 76 but must pass through that substantially oxygenfree atmospheric blanket to a position substantially adjacent or incontact with the bottom radiant wall 72 of the infrared generator bankbefore ,being ignited. For this purpose, as indicated above, the

Since a relatively low amount of volatile will be released in housingsection 14 and a maximum amount of volatile will be released in one ofthe other housing sections, section 18 for example, the amount of excessair pre-mixed with the gaseous fuel of each of the generator banks inthese housing sections must be controlled accordingly.

The incombustible products of combustion are evacuated in an air streamindicated by the arrows 78 flowing from atmosphere through the inletports 80 and 82 formed through the housing side walls 62 and 64,upwardly around each side of the generator bank between the supportmembers 78 into -an exhaust manifold 84 extending over the entire lengthof all four housing sections 14, 16 18 and 20 and from which uid ow isestablished through an outlet conduit 86 by an exhaust blower 88 poweredby a suitable electric motor 90 shown in FIGURE 2.

As is illustrated in FIGURE 1, pivotally adjustable batiies 92, 94, 96and 98 are provided within the exhaust manifold 84 to control therelative amount of air flowing through the inlet parts 80 and 82 of thehousing sections 14-20. This is essential to accommodate the varyingamounts of volatiles which are released from the coating in each of thehousing sections 14-20.

The radiant wall 72 dened by the radiant faces of generators 44 are ofsufficient width transversely of the direction of movement of the workpieces that the beams of infrared radiant energy emitted therefrom aresubstantially equal to or greater than the m-aximum Width of the workpieces transversely of their direction of movement and are locateddirectly above the path of work piece movement so that as a work piece76 moves beneath the generators 44, the work piece 76 successivelyintercepts and is irradiated by the beams from the generator banks overits entire top surface exposed to the generators 44. The intensity ofirradiation of the work pieces 76 and the energy absorbed by the workpieces 76 is sufficient to heat them to a temperature at which theliquid solvent in the coating will volatilize and the fluid finishapplied to the surface of the work pieces and exposed to the radiantfaces of the generators 44 will be cured. As explained above, thesolvents used in the uid finishes which will normally be dried in thisoven are highly combustible. As a cold work piece 76 passes beneath eachgenerator bank it will be gradually heated. Initially little or nosolvent will be vaporized. As the work piece 76 passes successivelybeneath each bank of generators in line, it will reach a temperature atwhich there is a maximum solvent vaporization. While the temper-ature ofthe Work piece will continue to increase so long as it is subjected toirradiation, the amount of solvent being vaporized will graduallydecrease from the maximum until, as the work piece passes from the beamof the last generator bank in line, it is perfectly dry and its coatingcompletely cured and no further solvent volatilization occurs. As thework piece 76 passes under the successive banks of generators 44 theignition temperature of the volatilized solvent will be reached, inaccordance with this invention by positioning the radiant faces ofgenerators 44 but two to three inches from the forward one of conveyor22 between rollers 26 and 28 and by providing exhaust blower 88 whichnot only removes the products of combustion (CO and CO2) from Vtheheating area, but also prevents secondary air from communicating withthe generators 44, a low oxygen atmospheric condition will exist betweenthe radiant Wall 72 defined by generators 44 and the coated surface 74of work pieces 76 carried by the endless conveyor 22. Therefore, becauseof this low or substantially oxygen free atmosphere, combustion of thecombustible volatiles cannot be supported close to the work pieces. Thevolatilized combustible solvent rises through this low oxygen atmosphereuntil it 4reaches the radiant wall 72 defined by the generators 44 andat that point it comes in Contact with the excess oxygen in premixedgaseous fuel and air which has sufficient oxygen to Vsupport combustionof the volatilized solvents as well as the fuel at the face of theradiant generators 44. The solvent thus, in effect, adds fuel to thecombustion process and in effect sustains and aids the irradiationeffect of the radiant generators. The positioning of the tile faces inclosely spaced relationship to the work pieces prevents externalsecondary air from entering into the combustion process so that theexcess oxygen in the pre-mixed gaseous fuel and air is substantially theonly source of oxidizing agent available to the combustible material.The exhaust blower 88 performs the function of withdrawing the productsof combustion CO and CO2 from the work area of the drying apparatus.Because of the suction effect of the exhaust blower 88, the inlets and82 do not provide additional oxygen for the combustion process. Thetotal amount of pre-mixed fuel and air supplied to each radiantgenerator input manifold such as 46, 48 and 50 can be controlled byappropriate control valves. By properly regulating the baffles 92 andthe pre-mixed fuel and air control valves, the amount of products ofcombustion which result from the combustion of the volatiles releasedfrom the work pieces as well as that lwhich results from combination ofthe pre-mixed fuel which products of combustion are evacuated from eachsection of heating area can be regulated so that all of the products ofcombustion will be uniformly evacuated from each section of heatingarea.

From the foregoing it will be readily apparent to one skilled in the artthat this invention provides infrared generators to cure the coating ofcoated work pieces which utilize the reflective properties of the workpieces to aid in the drying and curing the work piece coatings andadditionally utilize the volatiles released from the work pieces asadditional fuel for the radiant generators while eliminating theexplosion hazard. 'Ilhese attributes of the present invention areparticularly important because they permit a more eicient operation ofradiant heat generators in ovens of this type than that which hasheretofore been attainable.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristic thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. Apparatus for curing the coating of coated work pieces comprising ahousing, an endless work piece support conveyor extending longitudinallythrough said housing, said housing having air inlet openings at eachside of said conveyor to admit cooling air into said housing, at leastone bank of gas burning infrared generators, means supporting saidgenerator lbank in said housing above said endless conveyor in aposition to irradiate work pieces carried by said conveyor, an outletmanifold in said housing disposed above said generators and forming atop closure for said housing, means for inducing flow of cooling airinto said housing through said inlet openings upwardly along the side ofsaid conveyor and said radiant generators bank and into said outletmanifold over the top of s-aid generator bank supporting means and outto atmosphere to thereby cool said apparatus and evacuate the combustionproducts from the space between said generator bank and said conveyorwithout supplying air to said space.

2. The apparatus of claim 1 wherein said generator bank has a radiantwall spaced from said conveyor a distance in the order of but two tothree inches.

3. The apparatus of claim 1 together with at least one adjustable bafflein said outlet manifold for controlling 7 8 the distribution along saidhousing of the cooling air ad- 2,210,032 8/40 Hess 101--416 mittedthereinto. 2,220,928 11/40 Kienle et al 263-52 4. The apparatus of claim3, wherein said housing is 2,268,987 1/ 42 Hess etal 34-23 X comprisedof a plurality of sections and there are ad- 2,388,762 11/45 Powers263-8 justable baes for controlling the admission of cooling 5 2,884,7055/59 Flynn 117-46 X air into each of said housing sections. 3,015,479 1/62 Edberg et al 263-8 3,056,382 10/62 Glaser et al 117-46 ReferencesCited by the Examiner UNITED STATES PATENTS CHARLES SUKALO, PrimaryExaminer. 793,365 V3/'05 Rupley 117 46 10 FREDERICK L. MATTESON, JR.,JOHN I. CAMBY',

2,03 5,746 3/36 Hall 263-8 Examiners. T

1. APPARATUS FOR CURING THE COATING OF COATED WORK PIECES COMPRISING AHOUSING, AN ENDLESS WORK PIECE SUPPORT CONVEYOR EXTENDING LONGITUDINALLYTHROUGH SAID HOUSING, SAID HOUSING HAVING AIR INLET OPENINGS AT EACHSIDE OF SAID CONVEYOR TO ADMIT COOLING AIR INTO SAID HOUSING, AT LEASTONE BANK OF GAS BURNING INFRARED GENERATORS, MEANS SUPPORTING SAIDGENERATOR BANK IN SAID HOUSING ABOVE SAID ENDLESS CONVEYOR IN A POSITIONTO IRRADIATE WORK PIECES CARRIED BY SAID CONVEYOR, AN OUTLET MANIFOLD INSAID HOUSING DISPOSED ABOVE SAID GENERATORS AND FORMING A TOP CLOSUREFOR SAID HOUSING, MEANS FOR INDUCING FLOW OF COOLING AIR INTO SAIDHOUSING THROUGH SAID INLET OPENINGS UPWARDLY ALONG THE SIDE OF SAIDCONVEYOR AND SAID RADIANT GENERATORS BANK AND INTO SAID OUTLET MANIFOLDOVER THE TOP OF SAID GENERATOR BANK SUPPORTING MEANS AND OUT TOATMOSPHERE TO THEREBY COOL SAID APPARATUS AND EVACUATE THE COMBUSTIONPRODUCTS FROM THE SPACE BETWEEN SAID GENERATOR BANK AND SAID CONVEYORWITHOUT SUPPLYING AIR TO SAID SPACE.